Interesting. Did you simply replace the RG6 with the mic cable or did you also convert to low impedance balanced?
-Hal
The power Sub had a balanced input so it was indeed balanced to balanced. When heavy gauge copper is used in a Quad configuration, it only takes a few millivolts more of induced RF in one of the two balanced inputs to not be adequately rejected by some CMRR circuits. The cheaper methods using an IC as the differential input may boast a -60 DB CMMR for Hum/Noise or other induced EMI,
if they use 0.1 % resistors to null or balance the feedback networks. However within the substrate of the semi-conductor material itself within the IC, the integration process uses back-biased diodes to set the gain of subsequent stages. The best tolerances of these substrate diodes is 10%. Diodes act as detectors for RF. Thus in cheap products with cheap CMR stages, the best S/N for RFI is more like -20 dB. -20dB of CMRR may get you by in many environment, but not necessarily in a venue next door to a radio tower. The beauty of a quality balanced line transformer is that it simply can not pass
any RF.